The present invention pertains to the technical field navigation systems, and in particular to step-by-step navigation systems in which a vehicle or other movable body is guided from a starting point to a destination.
In recent years, onboard navigation systems for vehicles have become popular in Japan and some other countries. This is a high performance system, with a high definition display unit and a large volume memory device that allows easy display of the guiding route to the destination for the driver or the like with reference to prestored wide ranging map information. More specifically, for example, it has the following functions: the position of the vehicle itself is superimposed and displayed on the map shown on the display unit; the guiding route is displayed in a different color; and intersections or the like are expanded and displayed on the map. Consequently, the driver can easily check the position of the vehicle itself and the guiding route.
On the other hand, there is a type of navigation system that is equipped with a display unit that can only display simple characters or symbols or the like that displays the distance to the destination, the travel direction at an intersection, etc. with simple numeric data or arrows or the like instead of displaying a map. This simple navigation system is known as a step-by-step system or turn-by-turn system, and has been adopted in Europe, the U.S.A. and other locales.
The step-by-step navigation systems require only minimal functionality, and the device is inexpensive. This is an advantage. More specifically, the display unit does not require high performance, and there is also no need to have a large-capacity storage device that can store large amounts of map imagery.
Also, since the quantity of visual information displayed on the display unit is small, the driver watches and checks the display unit with less frequency. As a result, driving the vehicle becomes safer. This is also an advantage.
In recent years, a step-by-step navigation system has been developed that notifies the driver of the appropriate route as the driver is guided, the uneasiness of the driver due to the small quantity of information can be eliminated, and the system is highly convenient, as shown for example in Japanese Kokai Patent Application No. 2002-318135.
Even with such measures, however, the lack of guidance information in the step-by-step navigation system, due to its basic characteristic of displaying minimal information such as characters and symbols, etc., instead of displaying a map remains a factor. In many cases, drivers may be dissatisfied due to insufficient information and difficulty in understanding the guidance is unavoidable. For example, when guidance is performed at an intersection where the course should be changed by turning left/right, etc., it may be difficult to completely guide the driver using characters and symbols without displaying a map.